1. Field of Invention
The invention relates to methods and apparatus for adaptively controlling a series hybrid electric vehicle to obtain selected zero emission control.
2. Description of Related Art
The desire for cleaner air has caused various federal, state, and local governments to change their regulations to require lower vehicle emissions. Increasing urban traffic congestion has prompted a need for increases in public mass transit services. Many large cities use buses to transport people into, out of, and within traffic congested urban areas. Conventional buses use diesel powered internal combustion engines. Diesel engines produce emissions, including carbon monoxide, that contribute to air pollution. It is possible to refine cleaner diesel fuel. However, cleaner diesel fuel is more costly to refine and causes a corresponding increase in the cost of bus service.
Alternative fuels have been used to reduce emissions and conserve oil resources. Compressed natural gas has been used as an alternative fuel. Compressed natural gas does not produce as much power in conventional internal combustion engines as gasoline and diesel and has not been widely developed or accepted as an alternative to gasoline and diesel.
Additives have also been developed for mixing with gasoline to reduce emissions. Ethanol and MTBE have been added to gasoline to oxygenate the combustion of gasoline and reduce emissions of carbon monoxide. These additives, however, are believed to cause decreased gas mileage and, in the case of MTBE, to be a potential public health threat.
Electric vehicles have been developed that produce zero emissions. Electric vehicles are propelled by an electric motor that is powered by a battery array on board the vehicle. The range of electric vehicles is limited as the size of the battery array which can be installed on the vehicle is limited. Recharging of the batteries can only be done by connecting the battery array to a power source. Electric vehicles are not truly zero emitters when the electricity to charge the battery array is produced by a power plant that bums, for example, coal.
Hybrid electric vehicles have also been developed to reduce emissions. Hybrid electric vehicles include an internal combustion engine and at least one electric motor powered by a battery array. In a parallel type hybrid electric vehicle, both the internal combustion engine and the electric motor are coupled to the drive train via mechanical means. The electric motor may be used to propel the vehicle at low speeds and to assist the internal combustion engine at higher speeds. The electric motor may also be driven, in part, by the internal combustion engine and be operated as a generator to recharge the battery array.
In a series type hybrid electric vehicle, the internal combustion engine is used only to run a generator that charges the battery array. There is no mechanical connection of the internal combustion engine to the vehicle drive train. The electric traction drive motor is powered by the battery array and is mechanically connected to the vehicle drive train.
In present series type hybrid electric vehicles, there is a need to control the engine, generator and electric motor to produce zero emissions. The need to produce zero emissions occurs when the series type hybrid electric vehicle is propelled along a selected route or area where pollution emissions are not tolerated. Such areas include the inside of a building, a tunnel, a densely populated region, or other designated areas.
The invention provides methods and apparatus for adaptively managing the internal combustion engine, generator, and electric motor to produce zero emissions for a series type hybrid electric vehicle.
An exemplary embodiment of a series type hybrid electric vehicle according to the invention is controlled so that a generator set of the vehicle, including an internal combustion engine connected to a generator, creates zero emissions within a zero emission zone. As the vehicle approaches the zero emission zone, the internal combustion engine and generator increase the electrical charge of the battery array to a predetermined electrical level and are eventually turned off to prevent emissions from entering the zero emission zone. As the vehicle leaves the zero emission zone, the internal combustion engine and generator are warmed to a predetermined thermal level for a full capacity operation. When the internal combustion engine and generator reach the predetermined thermal level, they operate at full capacity to bring the electrical charge of the battery array to a predetermined electrical level. Thereafter, the vehicle operates under a normal operation.
According to an exemplary embodiment, a method for adaptively controlling the state of charge of a battery array of a series type hybrid electric vehicle having an internal combustion engine connected to a generator and at least one electric motor propelling the vehicle through the zone includes determining a zone, turning off the internal combustion engine and the generator before entering the zone, and turning on the internal combustion engine and the generator after leaving the zone.
According to another exemplary embodiment, a series type hybrid electric vehicle includes an internal combustion engine connected to a generator, a battery array receiving current at least from the generator, at least one electric motor receiving current from the battery array, the motor propelling the vehicle, and a controller that determines a zone, turns off the internal combustion engine and the generator before entering the zone, and turns on the internal combustion engine and the generator after leaving the zone.
Other features of the invention will become apparent as the following description proceeds and upon reference to the drawings.